The all-new Trek Base Heated Blackout Shirt is a new addition to our premium Trek Base series. We combined the heated technology from our popular Reactor Heated Vest to provide a low bulk, heated base layer solution thatâs next to the skin. Like other garments in the Trek Base series, this new base layer top utilizes fine merino wool bonded with Carbon Alloy® for unprecedented odor protection, our Silver Alloy⢠treatment to defend against bacterial growth, and our Fusix⢠technology treatment for additional odor adsorption. The Trek Base Heated Blackout Shirt gives hunters 3 different levels of on-demand heat to help them stay comfortable on the stand in any condition. The three levels of supplemental heat output are powered via a built-in USB power cable and easy, one-button control. The BE:1 Trek Base Heated Blackout Shirt can be powered by any 5V/2A battery or power bank (not included). This base layer can be worn as a normal base layer then as the temps drop you can crank the heat!